The invention relates to methods and systems for identifying methods and compositions which are effective in counteracting allergic reactions. More specifically, the present invention involves the use of cloned mast cells to test in vitro for the ability of compounds and compositions to interfere with the response of mast cells to allergens in vivo, by interference with the ability of mast cells to bind to IgE, by inhibition of the synthesis or secretion of allergic mediators, such as leukotrienes or prostaglandins by IgE-bound mast cells, or by deactivation of such mediators, e.g., by combination with or bonding to them.
Allergic persons or animals are afflicted with an over reaction of the body to the particular allergens to which the individual is allergic, such as pollen, dust, animal dander, etc. The allergic reaction is initiated by a stereospecific interaction involving the allergen, the mast cells and immunospecific materials which cause degranulation of the mast cells in the presence of the allergen, generally referred to in this application as immunoglobulins of the type IgE (also known as reagin or sensitizing antibodies). Binding to the IgE on the mast cell surface immunologically activates the mast cell, which then releases a variety of substances, including histamine, leukotrienes, and other components of what has traditionally been known as "slow reacting substance of anaphlaxis (SRS-A)," glycosoaminoglycans (e.g. heparin, chondroitin sulfate) serotonin, prostaglandins and/or other materials, depending on the type of mast cell involved. These substances affect the tissues in the locale of the affected mast cells, typically causing vasodilation, increased vasopermeability, non-vascular smooth muscle contraction, leucocyte infiltration, and destruction and repair of local tissue. See, e.g., R. A. Lewis, et al., "Mediation or Local Homeostasis and Inflammation by Leukotrienes and Other Mast Cell Dependent Compounds," Nature, 293:103 (1981), the disclosure of which is incorporated herein by reference.
The seriousness and type of the allergic reaction depends to some extent on the type and location of the mast cells involved. For example, when allergens are injected directly into the blood stream, the reaction can take place with mast cells located throughout the circulatory system. The release of histamine, leukotrienes, and other mediators, results in substantial vasodilation and loss of plasma flow. The affected individual can go into anaphylactic shock and die within minutes of the infusion of the allergen into the blood stream.
More localized instances of the allergic reaction include asthmatic attacks, where the allergen affects the tissue of the bronchioles in the lungs; "hay fever" symptoms of swelling and fluid leakage in the nasal tissues when the allergen contacts those tissues; and urticaria of skin tissues, resulting in "hives" when the allergen enters those tissues. Similar reactions can occur, with varying degrees of seriousness, where, because of infection, aging, or other factors, the body loses its immunological tolerance for its own tissues. In autoimmune diseases, the body's immunological defenses are activated against its own tissue, causing substantial destruction of the tissues involved. Autoimmune related diseases include rheumatic fever, acute glomerulonephritis, myasthenia gravis, and systemic lupus erythematosis. See, e.g., Guyton, Textbook of Medical Physiology, 77 et seq (5th Ed. 1976).
The treatment of chronically allergic individuals typically has been with antihistamines, to prevent or diminish the effect of the histamines released as a result of the allergic reactions. However, antihistamines are often ineffective against the actions of other mediator compounds released after the allergic reaction. Means have been lacking for identifying compounds which counteract such other mediators. Moreover, more effective materials for combating allergic type reactions described above can be developed by identifying those reagents which block the reaction between the allergen and the IgE receptors on the surface of mast cells, thus preventing the activation of such cells in the first place, which in turn prevents the release of histamine, leukotrienes, and other destructive mediator compounds. Until now, the only effective means for identifying the desired compounds has been through laborious, expensive, complicated bioassays, typically involving administration to lab animals, with subsequent analysis of reactions.
Another problem which has made treatment of allergies difficult is the inability to quantify sensitivity of mammals to allergens. Allergy specialists have not been able to accurately determine either the types of allergen to which individual mammals are sensitive, or the severity of the sensitivity, because prior to the present invention there was no accurate method to measure the precise degree of sensitivity to any particular antigenic material. Allergists have been left to crude skin tests, in which a variety of potential allergens are administered to an individual intradermally, and the existence and severity of allergic sensitivity is guesstimated from the appearance and size of the resultant wheals or erythema, i.e. area of the skin around the injection site which becomes inflammed after the injection of the allergen. Such tests are qualitative and subjective at best, and are not accurate, nor, in many cases, even repeatable.